Hook up an Apple iPhone to a touchscreen computer to allow full functionality of the phone by using the screen

My 13 yr old son has cerebral palsy. Very intelligent but limited motor functions. To use small devices like a cell phone are extremely challenging. trying to figure out a way to mirror an iphone screen onto a touch screen computer in order to enlarge it for him. idea would be to attach the phone to the computer and the computer to his wheel chair, powered from his battery. I like the iphone only for the large number of apps. would like to be able to "toggle" between using the phone and apps, to other functions such as ms office apps for school, listening/reading digitial books. Any ideas